Abstract
In the field study many types of drug-resistant E. coli, Shigella and Citrobacter were isolated by this laboratory. And seven types of transmissible drug-resistance factor were obtained; R(TC) R(SM), R(CM. TC), R(SM. SA), R(CM. SM SA), R(TC. SM. SA) and R(CM. TC.SM. SA). The R(CM) factor was segregated from (CM. TC) resistance of Sigella.
These factors were eliminated spontaneously from a host strain in high frequency. From the segregation of these factors, R(CM. SM. SA), R(SM. SA) and R(TC. SA) factors were found and not transferable by conjugation.
